Ventilation of tunnels.



PATENTBD 00T. 29, 1997.

Nm 869,297. s. u. DAVIDSON.

VENTILATION oP TUNNBLS.

APPLIOATONTILED JAN. 27, 1904.

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No. 869,297. PATENTBD 001.529.190?.

S. C. DAVIDSON. VENTILATION 0F TUNNELS.

APPLIOATION 'FILED un. 27, 1 904.

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SAMUEL GLELAND DAVIDSON, OF BELFAST, IRELAND.

VENTILATION oF TUNNELS.

Specification of Letters Patent.

Patented Oct. 29, 1907.

Application filed January 27, 1904-.. Serial No. 190,787.

To all whom "it may concern:

Be it known that I, SAMUEL CLELAND DAvIDsoN, a subject of the King of Great Britai'n and Ireland, residing in Belfast, Ireland, merchant, have invented certain new and useful Improvements in the Ventilation of Tunnels, of which the following is a specification.

My improvements relate more particularly to railway tunnels, but are applicable also to mines, large main sewers, or any tubular conduits or passages which are freely open to the atmosphere at both ends (hereinafter referred to as tunnels).

In railway tunnels a clear passage way for the train must always be kept freely open, throughout the entire length as also at each end of the tunnels, and when said tunnels pass through mountains or underrivers, or under cities where it is impracticable to have any or sufficiently large or numerous vertical shafts or iumes therefrom to insure suiiicient ventilation the air within said tunnels must in some cases be put into motion so that a through current is established from one end to the other whereby a flow of fresh air will enter the tunnel at one end and the exhaust air flow out at the opposite end, with suflicient velocity to maintain a certain standard of purity in the air within the tunnel. In such instances the methods hitherto generally preferred for setting up this necessary air current through the tunnels consists of various forms of air injecting apparatus at one end of the tunnel, in one of which for example an arch-like belt or lm of air is driven into the tunnel at a high velocity along the vertical sides and arched top of the tunnel portal, which must necessarily be bell-mouthed to a suiiicient enlargement to provide for the arch-like casing or chamber from which said air belt issues and at same time leave a clear space within said arch-like casing of corresponding size with the passage way for the trains through the tunnel itself. The air from said air belt on being injected into thetunnel at a high velocity creates also an induced flow of air through the train passage way within the arch of the air belt casing which mixes with the air from the belt, and the mixture then fiows through and out from the opposite end of the tunnel, but at a much slower velocity than that of the relatively smaller volume of air issuing from the belt. It is however well known that the power required to move a given volume of air increases in the ratio ofcthe square of the velocity of air from the belt which volume is usually about one half to two-thirds of the total volume of the air in motion through the tunnel, these proportions having been indicated in some practical tests which have been made'in tunnels ventilated in this way, and it has also been indicated that the injected air from the belt requires to have a velocity of injection equal to about 6,000 lineal feet per minute to produce a flow through the body of the tunnel of about one quarter of the initial velocity of the air belt injection, or only about 1500 lineal feet per minute, as much of the force of the injected air, while at its highest velocity, is wasted by impact and friction against the bell-mouthed sides of the tunnel portal. It is obvious therefore that to impart a velocity of 6,000 feet per minute to say one half of the total volume of air passing through the tunnel, will require 16 times more power than same volume would absorb if moved at one-fourth of that velocity, and 8 times more power than it would take to move double that volume or say the whole volume passing through the tunnel if it were practicable to impart direct impulsion to same. Hence an important saving in power would be effected if instead of applying the high initial velocity of say,6,000 lineal feet per minute to say one half of the total air current moving through the tunnel to produce a movement in same of only 1500 feet per minute, this same movement could be effected by having the initial impulsion velocity of the whole of the air current through the tunnel more nearly approaching that of its average rate of rflow through same. n

It is the obj ect of my invention to produce a sufficient air current through said tunnels to maintain the required purity of the air withinvsame with an important saving in power and at the same time avoid using the cumbersome appliances necessary for the injection v systems as hitherto employed at the portals of the tunnel.

According to my invention I produce an air current through tunnels by means of a fan or fans so arranged and located within the tunnel as not to interfere with any required freedom of passage therethrough and so that air is drawn directly from the tunnel into said fan or fans and discharged therefrom in a'direction which is either parallel with or at a slight angle to the axis or line of the tunnel, whereby a general ow of the` air contents of said tunnelis produced in the direction of the air discharge fromsaid fan or fans. Fans acting as f described may be arranged at intervals so as to act as relays one to the other whereby tunnels of any length 1 canvbe elliciently ventilated with a minimum cost of apparatus and at a minimumrequirement for power.

In applying my invention in one form to a comparatively short tunnel of, for example say 300 yards in length, I construct a recess in the side of the tunnel (similar to the shelter recesses ordinarily provided for workers in tunnels) at about 100 yards from the end of the tunnel at which the fresh air is to be drawn into it, and of sufficient height, width and depth back from the line of the tunnel side, as to` give ample room for placing afan therein, with driving motor attached to it, and space to get around it conveniently on all sides.

The type of fan which I preferably employ is `that described in the specification ofvLetters Patent granted to me and dated 27th.Novembler` 1900, but any other kind of fan may be used. Said fan being thus located to one side of the line of the tunnel tormsno obstruction to the passage oi trains through same and its inlet opening is so arranged as to draw its air supply from the tunnel, and its discharge is so directed as to inject this air' back into the tunnel either parallel with the axis thereof, or at as slight an angle therewith as is practicable in the direc-tion that the air current is to flow through the tunnel. The result of this arrangement is that the suction into the tan and the discharge therefrom act in unison towards setting up a fiow through the tunnel, the suction helping to draw the fresh air in from the inlet portal of the tunnel up to the fan,

'and the discharge rom the fan acting as an injector' to propel the air in the tunnel from the ian towards the exhaust portal, so that both inlet and discharge oi the fan have a combined operative ei'i'ect towards putting the air within the tunnel into motion, and this double action I have found will produce the same velocity oi air flow within the tunnel as would be got by an equal size of ian driving the air at twice the velocity into one end of the tunnel on the air-belt injection system hereinbefore described, and for much less power than required by such air-belt system ot' injection.

According to a further modification oi my invention and in order to apply same effectively to long tunnels, of say one or more miles in length, the above described combination of recess and ian within the tunnel is repeated at intervals along the tunnel. The whole length of the tunnel can thus be divided into sections, at the end of each of' which a combination oi recess and fan operates as a -relay on the one preceding it, and assuming that the fans are each of the same size, and operating with the same power, then each succeeding relay will reinforce the velocity of the air current flowing into, through, and out of the tunnel, with a minimum of loss due to friction by reason o the propelling power being added by a succession ofrelays and thereby with a minimum oi shock, and as almost any number of fans can thus be employed, to simultaneously operate on the air within the tunnel, it becomes practicable to employ moderate sizes of fans in sufficient number, to total up a united area ot' inlet thereto, and discharge therefrom, to be equal to the entire cross section oi the tunnel, so that the velocity of flow through the fans need only exceed the velocity of flow through the tunnel, by just so much as will replace the loss of velocity due to friction of the main current along the sides of the tunnel, which at the comparatively low velocityusually required (of say about 150() lineal feet per minute) does not amount to much, when the required impulsion is imparted to the current by relay, hence by my hereindescribed invention the required flow of air through the tunnel can be accomplished with a minimum of initial velocity through the fans, and therefore With a minimum of power for driving the fans, which driving power preferably consists of direct coupled electric motors, so controlled from either end of the tunnel, that all the motors and fans can be either started simultaneously, or individually, as required. For instance, when a train is going through the tunnel all the fans could be run at full power simultaneously and maximum ventilation maintained till the train had passed through,

after which the operation of one or more fans at a re- -duced speed would be sufficient to clear out the remnant of smoke and impurities remaining in the tunnel, and to keep the air in it pure until the next train entered, when full speed and power could again be applied.

Reference to the accompanying drawings will more fully explain the nature of my invention and how the same is carried into effect.

Figure 1 is a sectional plan of a short length of tunnel showing the employment therein of a single fan only. Fig. 2 is a cross sectional elevation online Y-Z o1' Fig. l. Fig. 3 is a sectional plan of a tunnel showing two side recesses and fans therein, both acting on the same side o the tunnel, and in the same direction, whereby the second fan acts as a relay to the first fan. It is obvious that a iurther numb er of fans may be similarly applied as additional relays along the tunnel, according to its length. Fig. 4 is an enlarged sectional plan, showing a side recess in the tunnel, with a fan and its inlet opening located therein and the fan discharge duct carried along the outer side of the tunnel wall and terminating with a cast iron wall box which forms the discharge nozzle from said discharge duct into the tunnel. Fig. 5 is a side elevation looking in the direction of the arrow shown on Fig. 4. Fig. 6 is a sectional plan of tunnel showing the combination of side recesses and ians applied in alternating order on both sides of the tunnel.

The letters employed to indicate the various parts are the same in each figure and are as follows A` A indicates the tunnel. B B the inlet portal of said tunnel. C C the exhaust portal therefrom. D D railway track through the tunnel. E E recesses in the sides ofthe tunnel. F F fans located within the side recesses E E. G G electric motors direct coupled to lan shaft for driving same. H H the inlet opening or suction eye oi fan. .l .l discharge duct from ian. K K the cast iron wall box forming discharge nozzle from the discharge ducts .T .l into the tunnel A A.

L M is a dotted line indicating the axis oi the discharge from the wall boxes K K which discharge forms a slight or acute angle L M N with the axis ofthe tunnelA Referring to Fig. 1, on the fan being started its operative effects are as followsz-An inflow of air takes place irom the tunnel through the entrance to the side recesses (E) into the inlet opening or suction eye (H) to the fan (F) and thence is discharged through duct (J K) back into the tunnel (A) along the line (LM) as indicated by arrows, which discharge being in the direction of the tunnel portal (C) rnpinges into and gradually mixes with the air of the tunnel, and thereby imparts motion to it in the direction of the exhaust portal (C) whereby an induced current into and along the tunnel is created from the inlet portal (B) from which induced current the ian suction draws its supply, and thereby also assists the flow of the air irom the inlet portal (B) up to the side recess in which the fan is located.

The above is the simple action that takes place in short tunnels where only one fan is employed, as represented in Fig. 1, but where two o1' more fans are employed, as indicated in. Figs. 3 and G, the second ian, which is further along the tunnel from the inlet portal than the first ian, acts as a relay thereto, and its operative effect upon the air within the tunnel being similar it imparts to same an additional impulse towards the portal (C) and the same action takes place with any iurther number of fans which may be thus employed as relays in tunnels of greater length. In Fig. 3, the side recesses and lans are shown as employed on only one side oi the tunnel, but when local conditions permit of their being employed on both sides I preferably arrange them in alternating oroler7 as shown in Fig. G.

What I claim as my invention and desire to secure by Letters Patent is:-

l. A tunnel having means for moving the column of air contained therein in a direction lengthwise of the tunnel, such means comprising air-forcing means discharging into such column at a point between the ends of the tunnel, said means delivering a blast ofpair of a cross-section so much smaller than that of said column, that the quantity of air delivered by said blast shall be insufficient to place the sides of said column under any considerable radial pressure, said blast being directed -in such manner as t0 move the latter in the required direction` 2. A tunnel having means for moving the column of air contained therein in a direction lengthwise of the tunnel, such means comprising a plurality of air-forcing means discharging into such column at dilerent points in the length of the tunnel, said means delivering blasts of air of a cross-section so much smaller than that of said column, that the quantity of air delivered by said blasts shall be insuincient to place the sides of said column under any considerable radial pressure, said blasts being directed in such manner as to move the latter in the required direction.

2. A tunnel having air-forcing means' adapted to draw a portion of the m'ain column of air therefrom, and to discharge it into said column at a point between the ends of the latter in such manner as to move the column in a direction lengthwise of the tunnel.

4. A tunnel having a plurality ot' air-forcing means at different points in its length, each ot said means adapted to draw a portion of the main column of air therefrom, and to discharge it into said column at points between the ends of the latter in such manner as to move the latter in a direction lengthwise of the tunnel.

A tunnel having a plurality of air-forcing means at different points in its length, each of said means adapted `to draw a portion of the main column of air therefrom,

and to discharge it into said column at points between the ends of the latter in such manner as to move the latter in a direction lengthwise of the tunnel, one of said means being adapted to act upon said column before the effect of the preceding means is exhausted.

6. A tunnel having a plurality of centrifugal fans arranged at intervals within the tunnel, each of such fans being adapted to withdraw a portion of the main column ci air and discharge it into said column at points between the ends of the latter in the direction in which the column is to be moved, said fans being so arranged so that each fan acts upon the column before the effect of the preceding fan is exhausted, whereby the entire column is maintained in movement.

7. A tunnel having means for moving the column of air contained therein in a direction lengthwise of the tunnel, such means comprising a plurality of air-forcing means discharging into such column at different points in the length of the tunnel, said means delivering blasts of air of a cross-section so much smaller than that of said column, that the quantity of air delivered by said blasts shall be insuliicient to place the sides of said column under any considerable radial pressure, said blasts being directed in effect into the center of the column, and in a direction substantially parallel therewith.

S. Atunnel having a plurality of air-forcing means at different points in its length, each of said means adapted to draw a portion of the main column of air therefrom, and to discharge it into said column at points between the ends of the latter in such manner as to move the latter in a direction lengthwise of the tunnel, said blasts being in effect directed into the center of said column, and in a di rection substantially parallel therewith.

SAMUEL CLELAND DAVIDSON.

Witnesses GEORGE GooLD WARD, FnEDERicr; GEORGE MCGUIRE. 

